Apparatus for Minimally-Invasive Prevention and Treatment of Hydrocephalus and Method for Use of Same

ABSTRACT

An apparatus for minimally-invasive, including non-invasive, prevention and/or treatment of hydrocephalus and method for use of the same are disclosed. In one embodiment of the apparatus, a housing is sized for superjacent contact with a skull having a fontanel. Within the housing, a compartment includes a pressure applicator, such as a fluid-filled bladder, under the control of a pressure regulator. The pressure applicator is configured to selectively apply an external pressure to the fontanel. The compartment includes a pressure sensor configured to measure intracranial pulse pressure of the fontanel. Further, in one embodiment, the apparatus can cause pulse pressure modulation by adjusting the intracranial pulse pressure via the pressure applicator. This enables a non-invasive measurement of the pulse pressure and modulation thereof in infants, for example.

PRIORITY STATEMENT & CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/620,189 entitled “Apparatus for Minimally-Invasive Prevention andTreatment of Hydrocephalus and Method for Use of Same” filed on Dec. 6,2019 in the name of Frederick H. Sklar, now U.S. Pat. No. 11,154,695issued on Oct. 26, 2021; which is the National Stage of, and therefore,claims the benefit of the Jun. 7, 2018 filing date of internationalapplication PCT/US2018/036558, which designates the United States, filedin the name of Frederick H. Sklar and entitled “Apparatus forMinimally-Invasive Treatment of Hydrocephalus and Method for Use ofSame”; which claims priority from U.S. Patent Application Ser. No.62/516,359 entitled “Apparatus for Minimally-Invasive Treatment ofHydrocephalus and Method for Use of Same” filed on Jun. 7, 2017 in thename of Frederick H. Sklar; all of which are hereby incorporated byreference, in entirety, for all purposes.

TECHNICAL FIELD OF THE INVENTION

This invention relates, in general, to the treatment of hydrocephalusand, in particular, to an apparatus for the minimally-invasive,including non-invasive, prevention and/or treatment of hydrocephalus inpremature infants, term infants, and other individuals and method foruse of the same.

BACKGROUND OF THE INVENTION

Cerebrospinal fluid (CSF) is made within the ventricles of the brain andpercolates through the ventricular system in response to brainpulsations. In normal circumstances, CSF exits in the fourth ventricleand circulates over the surface of the brain and around the spinal cordto be absorbed into the venous system. Hydrocephalus is a disease thatis assumed to occur when the absorption mechanisms are not inequilibrium with the rate of CSF production. The disease ischaracterized by enlargement of the cerebral ventricles, abnormally highintracranial pressure (ICP), and large heads in children. In addition,the elderly can develop so-called normal pressure hydrocephalus (NPH).In addition, approximately 22% of premature infants have germinal matrixhemorrhages, commonly referred to as intraventricular hemorrhages (IVH),and many of these babies develop post-hemorrhagic hydrocephalus.Approximately 50% of babies with IVH develop ventricular enlargement,and half of these clearly have progressive hydrocephalus, frequentlyrequiring neurosurgical treatment. The other half are said to haveso-called arrested hydrocephalus, although slowly-progressive, activehydrocephalus remains a possibility.

The prevailing treatment options for hydrocephalus are limited. Somepatients develop obstructive hydrocephalus as a result of anintracranial tumor distorting or blocking CSF pathways. Treating thetumor frequently corrects the hydrocephalus problem. Approximately 90%of children with posterior fossa tumors and hydrocephalus do not requirepermanent shunts for their hydrocephalus once the tumor has beenremoved. Some selected patients with obstructive hydrocephalus such asaqueductal stenosis can benefit from endoscopic third ventriculostomy(ETV). However, the majority of patients with hydrocephalus requireshunt surgery.

This surgical treatment involves the implantation of a Silastic®device—a cerebrospinal fluid shunt (CSF shunt)—to divert fluid from thebrain ventricles to another body compartment, where the CSF can beabsorbed into the venous system. Shunt surgery has had a tremendouspositive impact on neurosurgery and represents a significant clinicaladvancement of the 20th century. Shunt surgery has become the mainstaytreatment of hydrocephalus. There are numerous valves and shunt systemsavailable in the marketplace. Some utilize relatively simplisticpressure differential valves; some are regulated by flow; and some areprogrammable. There are reservoirs, antibiotic treated components, andanti-siphon devices. Shunts can malfunction, obstruct, break, or getinfected. Thirty percent of shunts fail in the first year afterplacement. Over-shunting is common, and many patients experienceheadaches from intracranial hypotension. Some patients can developsubdural hematomas as a result of the ventricular decompression andtearing of bridging veins.

CSF absorption is a sensitive function of ICP; it increasessignificantly as pressure is increased. Even in communicatinghydrocephalus, CSF increases with increasing ICP, although not as much.CSF production is essentially independent of ICP, or may decreaseslightly at very high pressures. In other words, there is an absorptivereserve in which absorption exceeds production, and this is maintainedeven in hydrocephalus.

Ventricular pulsations may be particularly important in the developmentof hydrocephalus. Augmentation of the ventricular pulse pressure ingoats with pulsating balloons synchronized to the cardiac cycle causeshydrocephalus. The pulse pressure in the ventricle with the shuntcatheter is smaller than in the other lateral ventricle. Scans show thatthe shunted ventricle is typically smaller than the other side.Subgaleal shunts divert ventricular CSF into a pocket under the scalp,effectively treating the hydrocephalus, at least temporarily.Subarachnoid hemorrhage patients frequently develop hydrocephalus.Ventricular drainage is frequently used in these patients, and theintracranial pulsations have been noted to gradually increase eventhough ICP is held constant.

It is possible that shunts work by dampening the ventricular pulsepressure (PP). Diversion of CSF into the peritoneal cavity, pleuralcavity, heart, gall bladder, or subgaleal space may be only anepiphenomenon. Further, shunts may be effective in treatinghydrocephalus only because a small volume of CSF is displaced out of theventricle with every heartbeat, therefore reducing the intraventricularpulse pressure. Shunts may work simply because they are shock absorbers.Numerous mathematical models of the CSF system have been suggested andsome more recent studies draw parallels with electrical circuitrysuggest that increases in ventricular pulsations, indeed, causehydrocephalus.

In newborns with an open fontanel, the intracranial pulsations can bemonitored and modulated through the fontanel without invasive surgicalimplantation of an intracranial device. Accordingly, hydrocephalus canlikely be treated in these infants without surgery, at least until thefontanel begins to close. In premature infants with intraventricularhemorrhage (IVH), who are at risk for developing post-hemorrhagichydrocephalus, not only can hydrocephalus be treated with PP modulationin infants who already have the disease, but it can also be preventedwith PP modulation that offsets the gradual increases in meanintracranial PP during the days, weeks, or months subsequent to the IVH.Advances in medical science are needed to treat hydrocephalus,particularly in premature infants.

SUMMARY OF THE INVENTION

It would be advantageous to achieve an advanced, non-surgical devicethat can prevent and treat post-hemorrhagic hydrocephalus in prematureinfants, as well as treating other forms of hydrocephalus in babies withan open fontanel. It would also be desirable to enable a medical-basedsolution that mitigates the enlargement of the cerebral ventricles andabnormally high intracranial pressure (ICP), particularly in prematureinfants. To better address one or more of these concerns, an apparatusis disclosed for the minimally-invasive, including non-invasive,prevention and treatment of hydrocephalus, in premature infants andothers and a method for use of the same. In one implementation, theapparatus modulates intracranial pulse pressure (PP) though thefontanels of premature and term infants.

The PP is the arithmetic difference between the peak pressure in systoleand the lowest pressure in diastole. The terms “pulse pressuremodulation” are being used to describe a therapeutic technique thatmeasures the intracranial pulse pressure and adjusts it by eitherreducing or increasing the intracranial PP according the clinicalsituation. Moreover, a device that allows non-invasive measurement ofICP and intracranial PP in babies with open fontanels would be a usefulclinical tool, not only for patients in neonatal intensive care unitsbut also older infants with open fontanels and ICP issues.

In one embodiment of the apparatus, a housing is sized for superjacentcontact on a premature infant skull having a fontanel. Within thehousing, a compartment includes a pressure applicator, such as afluid-filled bladder, under the control of a pressure regulator. Thepressure applicator is configured to selectively apply an externalpressure to the fontanel. The compartment includes a pressure sensorconfigured to, in one embodiment, measure displacement, includingpulsations, of the fontanel. The apparatus determines intracranial PP.Further, in one embodiment, the apparatus can cause pulse pressuremodulation by adjusting the intracranial pulse pressure via the pressureapplicator. This enables a non-invasive measurement of the pulsepressure and modulation thereof in infants, for example. Morespecifically, in one embodiment, to reduce intracranial PP in order toprevent or treat hydrocephalus after IVH, the apparatus monitorspulsations of the fontanel and responds to intracranial pressureincreases during systole with relaxation of the pressure applicator,which may be a fluid-filled bladder within a closed component with aventral opening, positioned on the fontanel thereby reducing thesystolic pressure. During diastole, the fluid-filled bladder is gentlyrefilled, thereby increasing the diastolic pressure. The cumulativeeffect of this cyclical process would work to decrease the intracranialPP. The mean ICP will likely not change, or it may decrease. In thissetting, the apparatus may include a solenoid pump and controllersoftware to modulate the intracranial PP.

Clinical conditions may exist in which augmentation of the intracranialPP may be desirable, such as to increase cerebral blood flow (CBF). Insuch a setting, the apparatus may function to withdraw fluid from thebladder during diastole and reinject this volume back into the bladderduring systole. The cumulative result of this process will increaseintracranial PP. These and other aspects of the invention will beapparent from and elucidated with reference to the embodiments describedhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages of thepresent invention, reference is now made to the detailed description ofthe invention along with the accompanying figures in which correspondingnumerals in the different figures refer to corresponding parts and inwhich:

FIG. 1 is a functional block diagram depicting one embodiment of anapparatus for the minimally-invasive, including non-invasive, preventionand treatment of hydrocephalus in premature infants, term infants, andother individuals, according to the teachings presented herein;

FIG. 2 is a functional block diagram depicting another embodiment of anapparatus for the minimally, invasive, including non-invasive,measurement of ICP and modulation of intracranial PP as a prevention andtreatment of hydrocephalus in premature infants, term infants, and otherindividuals, according to the teachings presented herein;

FIG. 3 is a top plan view depicting one operational embodiment of theapparatus of FIG. 1 and FIG. 2;

FIG. 4 is a top plan view depicting the operational embodiment of theapparatus of FIG. 3 in ghost to demonstrate a placement of the apparatuson the skull of a premature infant;

FIG. 5 is a side elevation view depicting the operational embodiment ofthe apparatus of FIG. 3 on the skull of the premature infant;

FIG. 6 is a bottom plan view depicting the operational embodiment of theapparatus of FIG. 3;

FIG. 7 is a top plan view depicting another operational embodiment ofthe apparatus of FIG. 1 and FIG. 2;

FIG. 8 is a side elevation view depicting another operational embodimentof the apparatus of FIG. 7;

FIG. 9 is a top plan view depicting the operational embodiment of theapparatus of FIG. 7 in ghost to demonstrate a placement of the apparatuson the skull of a premature infant;

FIG. 10 is a side elevation view depicting the operational embodiment ofthe apparatus of FIG. 7 on the skull of the premature infant, held inplace with a custom knit cap;

FIG. 11 is a top plan interior view depicting the operational embodimentof the apparatus of FIG. 7 with components selectively removed to revealthe interior;

FIG. 12 is a bottom plan view depicting the operational embodiment ofthe apparatus of FIG. 7;

FIG. 13 is a side perspective view depicting one embodiment of a centralcompartment, which forms a portion of the apparatus of FIG. 7;

FIG. 14 is a top plan view depicting the central compartment of FIG. 13;

FIG. 15 is a bottom plan view depicting the central compartment of FIG.13;

FIG. 16 is a side perspective view of one embodiment of a bladder, whichforms a portion of the apparatus of FIG. 7;

FIG. 17 is a top plan view of one embodiment of a position detector,which forms a portion of the apparatus of FIG. 7;

FIG. 18 is a top plan view of one embodiment of fluid power components,which form a portion of the apparatus of FIG. 7;

FIG. 19 is a side elevation view of the fluid power components of FIG.18;

FIG. 20 is a longitudinal cross-sectional view depicting the operationalembodiment of the apparatus of FIG. 7;

FIG. 21 is a transverse cross-sectional view depicting the operationalembodiment of the apparatus of FIG. 7;

FIG. 22 is a fluid power schematic diagram depicting of anotherembodiment of portions of a pressure regulator and the compartment, bothof which form components of the apparatus;

FIG. 23 is a mechanical power schematic diagram depicting of a furtherembodiment of portions of a pressure regulator and the compartment, bothof which form components of the apparatus;

FIG. 24 is a functional block diagram depicting one embodiment of acontroller, which forms a component of the apparatus;

FIG. 25 is a flow chart diagram depicting one embodiment of a method forthe minimally-invasive, including non-invasive, prevention and treatmentof hydrocephalus in premature infants, term infants, and otherindividuals, according to the teachings presented herein;

FIG. 26 is a flow chart diagram depicting another embodiment of a methodfor the minimally, invasive, including non-invasive, measurement of ICPand modulation of intracranial PP as a prevention and treatment ofhydrocephalus in premature infants, term infants, and other individuals,according to the teachings presented herein; and

FIG. 27 is a flow chart diagram depicting one operational embodiment ofa method for the minimally, invasive, including non-invasive,measurement of ICP and modulation of intracranial PP as a prevention andtreatment of hydrocephalus in premature infants, term infants, and otherindividuals, according to the teachings presented herein.

DETAILED DESCRIPTION OF THE INVENTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts, whichcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention, and do not delimit the scope of the presentinvention.

Referring initially to FIG. 1, therein is depicted one embodiment of anapparatus 10 for minimally-invasive, including non-invasive, preventionand treatment of hydrocephalus in premature infants, term infants, andother individuals. The apparatus 10 is sized for superjacent contact ona premature infant skull, for example, having a fontanel F. Theapparatus 10 includes a compartment 12, a pressure regulator 14, and acontroller 16. The compartment 12 may be selectively adjustable or fixedand configured to selectively apply pressure via pressure applicatorsuch as a bladder, for example, under control of the pressure regulator14, to the fontanel F. The pressure applicator may operate underhydraulic actuation, mechanical actuation, or a combination thereof. Thecompartment may then measure intracranial pulse pressure (PP) at thefontanel F and, if clinically applicable, pulse pressure modulate. Thecontroller 16 is interconnected communicatively with each of thecompartment 12 and the pressure regulator 14.

FIG. 2 depicts another embodiment of the apparatus 10 for minimallyinvasive, including non-invasive, monitoring of intracranial pressure(ICP) as well as intracranial PP, in addition to prevention andtreatment of hydrocephalus in premature infants with intraventricularhemorrhage (IVH) or in other babies with open fontanels who havehydrocephalus or intracranial hypertension. As shown, the compartment 12may be a central compartment 20 securing a pressure applicator depictedas a bladder 22, which may be a form of a sealed vessel, and a pressuresensor depicted as a disk pressure transducer 24 therein. The pressureregulator includes a fluid reservoir 26 fluidly coupled to the bladder22 by tubing 28 with a solenoid pump 30 and a magnet piston 32 as wellas valves 34, 36 controlling the fluid flow between the bladder 22 atthe compartment 12 and the fluid reservoir 26. The controller 16 isdepicted as a microcontroller 38 and, as shown, is interconnectedcommunicatively with each of the compartment 12 and the pressureregulator 14.

The disk pressure transducer 24 may measure displacement, includingpulsations, of the fontanel F. The apparatus 10 may determineintracranial PP in response to the displacement of the fontanel F. Inone embodiment, to reduce intracranial PP in order to prevent or treathydrocephalus after IVH, the apparatus 10 monitors pulsations of thefontanel F and responds to intracranial pressure increases duringsystole with relaxation of the fluid-filled bladder 22, positioned onthe fontanel F thereby reducing the systolic pressure. During diastole,the fluid-filled bladder 22 is gently refilled, thereby increasing thediastolic pressure. The cumulative effect of this cyclical process wouldwork to decrease the intracranial PP. The mean ICP will likely notchange, or it may decrease.

Clinical conditions may exist in which augmentation of the intracranialPP may be desirable, such as to increase cerebral blood flow (CBF). Insuch a setting, the apparatus 10 may function to withdraw fluid from thebladder 22 during diastole and reinject this volume back into thebladder 22 during systole. The cumulative result of this process willincrease intracranial PP.

Referring now to FIG. 3 through FIG. 6, the apparatus 10 includes ahousing 50 sized for superjacent contact on a premature infant skull Shaving the fontanel F. It should be appreciated that although apremature infant skull S is depicted for illustrative purposes, theapparatus 10 may be utilized with premature infants, term infants, andother individuals. The housing 50 is configured to fit within a capformed by a tube of stretchable material closed at one end; the otherend of the tube being dimensioned for a close fit about the prematureinfant skull. As shown, the housing includes an upper plate 52, a lowerplate 54, and a vertical sidewall 56 therebetween. A gel pad 58 locatedon the lower plate 54 contacts the premature infant skull S. An opening60 through the lower plate 54 and the gel pad 58 is sized for thefontanel F. As previously alluded, the housing 50 secures thecompartment 12, the pressure regulator 14, and the controller 16therein.

A battery compartment door 62 is positioned in the upper plate 52 toprovide access to a battery compartment. A locking knob 64 extends fromthe compartment 12, which may include a central compartment 20, andprovides for the placement of the compartment 12, including extensionfrom the lower plate 54 of the housing 50 and retraction into the lowerplate 54 of the housing 50. As previously mentioned, in otherembodiments, the compartment 12 and the central compartment may bestatic or utilize a different mechanism for determining and maintainingposition. A power switch 66, which is located in the upper plate 52,enables a user to turn the apparatus 10 ON and OFF. A position userinterface 68, which is also located in the upper plate 52, enables auser to mark the position of the apparatus relative to the prematureinfant skull S and the fontanel F. Various displays 70 are positioned inthe upper plate 52. In the illustrated embodiment, the displays 70include a position monitor 72, an ammeter display 74, and a wirelesssignal strength indicator 76.

The compartment 12 may traverse the housing 50 from the upper plate 52to the lower plate 54. The locking knob 64 is coupled to the centralcompartment such that the locking knob 64 is superjacent to the upperplate 52. The locking knob 64 is configured to selectively adjust thecompartment 12 to extend from the opening 60 and to retract within theopening 60. The central compartment 20 may house a pressure applicator88 and a pressure sensor 90. It should be appreciated that although aparticular device configuration with respect to inputs and outputs isshown with respect to the apparatus 10, other device configurations arewithin the teachings presented herein and any device configurationselected will depend on multiple factors.

Referring now to FIG. 8 through FIG. 22, in another embodiment, theapparatus 10 includes a housing 100 sized for superjacent contact on apremature infant, for example, skull S having the fontanel F. Thehousing 100 is configured to fit within a stretch knit cap 102, tailoredfor a close fit about the skull S of the premature infant or otherindividual. The stretch knit cap 102 attaches to a superior-lateralconvexity surface 104 of housing 100. As shown, the housing 100 alsoincludes a contoured upper plate 106, a similarly curved lower plate108, and an intervening curved sidewall 110 that contains a fluidreservoir 26 therein, which may encircle the perimeter of the apparatus10. A gel pad 112, located on the inferior surface of the lower plate108, contacts the premature infant skull S. The gel pad includes anopening 114 therethrough. The gel pad 112 may have a slightly adhesivesurface which helps to keep the apparatus from becoming dislodged, onceit has been correctly positioned. A clover leaf-shaped opening 116through lower plate 108 and the opening 114 through the gel pad 112 arepositioned and sized to approximate the fontanel F. As previouslyalluded, the housing 100 contains a central compartment 20, which mayopen inferiorly. Within the central compartment 20 is the inflatablefluid-filled bladder 22 and the disk pressure transducer 24. Adjacent tothe central compartment 20 is the solenoid pump 30, valve 34, valve 36,and the microcontroller 38 therein. Although in FIGS. 8 through 22, thefluid-filled bladder 22 is described with reference to hydraulicactuation, the actuation may occur mechanically as will be discussedhereinbelow.

Three battery compartment doors 118, 120, 122 are positioned in theupper plate 106 to provide access to the respective batterycompartments. It should be appreciated that the power requirements ofthe apparatus 10 may vary and the type and number of batteries or otherpower source will depend on various engineering factors and the numberof battery compartment doors may differ than the illustrated embodiment.Water or another fluid is introduced into the fluid reservoir 26 throughone of two ports 124, 126 while the unused port 124, 126 allows theextraction of air from the internal plumbing system.

In one operational embodiment, prior to placing the device 10 on anindividual's head, the cranial sutures adjacent to the fontanel F aremarked by the care provider with ink containing metallic particles.Approximately 2-3 cm of each suture adjacent to the fontanel F aremarked, including the superior metopic, rostral sagittal, and bothcoronal sutures.

In one embodiment, the care provider then applies the apparatus 10 overthe fontanel F, adjusting its position until the metopic-sagittal andthe bicoronal axes are aligned according to a position detector 128 onthe upper plate 106. As best illustrated in FIG. 17, the positiondetector 128 has four groups of three LED lights that are arranged toindicate the corners of the fontanel F: front and back, and right andleft, respectively. In each group, a central green LED is positionedbetween two yellow LEDs. Each of the twelve LEDs 130 correspond to aspecific capacitance position sensor 132, 134, 136, 138 located withinthe lower plate 108 adjacent to opening 114 and the central compartment20. In one embodiment, the goal is to position the center capacitancesensor of each group 132, 134, 136, 138 over its respective cranialsuture. The remaining two sensors in each group 132, 134, 136, 138 arepositioned closely adjacent to the center sensor (one on each side ofthe central sensor). For the coronal sutures, the two groups of threecapacitance sensors each form a gentle arc positioned approximately in asagittal plane. For the metopic and sagittal sutures, the two groups ofthree sensors are also arranged in arcs generally oriented in thecoronal plane. When the apparatus 10 is placed onto the head and anON-OFF switch 140 is activated, the microcontroller 38 measures theelectrical signal from each sensor of each group 132, 134, 136, 138,identifying the relative proximity to the underlying suture marked withmetallic ink. The microcontroller 38 accordingly lights that LED in eachof the four groups of the LEDs 130 with the highest signal. When theposition of the apparatus 10 has been adjusted so that all four of thegreen center LEDs are lit, a larger, square-shaped green LED in thecenter of the position detector 128 is lit by the microcontroller 38,and the previously lit adjacent, square-shaped red LED will go off. Thecare provider then pushes a button 142, just rostral to the positiondetector 128, to indicate to the microcontroller 38 this baselinepositioning of the apparatus 10 over the cranial sutures. Further, themicrocontroller 38 activates an alarm system to detect if the apparatus10 has dislocated from its baseline position. If it has becomedislodged, a remote alarm is triggered, so that the apparatus 10 can berepositioned.

Spaced around the curvilinear perimeter of the apparatus 10 may be anEKG lead and an EKG ground, each attached to the ventral surface of thegel pad 112. A second EKG lead may be located on the inside surface of astretch “sweatband,” sized to fit a premature infant's forearm or lowerleg above the ankle, for example. The cranial EKG lead and ground may beconnected directly to the microcontroller 38, located within the housing100, and the limb lead communicates wirelessly so that the QRS complexcan be recorded by the computer to provide an estimate of the onset ofsystole. A green LED light on the limb lead housing may indicate thatwireless connection has been made with the apparatus and that EKG isbeing received. A red LED light may indicate when the battery needs tobe replaced or recharged. A miniature pulse oximeter may be incorporatedinto the gel pad interface to monitor the patient's oxygen saturation.In another embodiment, pulse oximetry can alternatively be used todetermine cardiac systole.

Inside the housing 100 of the apparatus 10 is the central compartment20, which may resemble the shape of a four leaf clover. Approximatelycentered on the fontanel F, the central compartment 20 in one embodimentis comprised of three concentrically oriented clover-leaf structures144, 146, 148 with respective vertical walls 150, 152, 154 are in closeapposition. In addition, the central compartment 20 includes theinflatable bladder 22 and the disk pressure transducer 24. Moreparticularly, a continuous clover-leaf outer wall 156, which is fixed tothe upper plate 106 and extends to the lower plate 108, is provided. Anintermediate, discontinuous, cover-leaf component 158 includes fourseparate vertical sliders 160, 162, 164, 166 that may be independentlyraised or lowered so that each slider 160, 162, 164, 166 is in contactwith the underlying scalp.

A clover leaf-shaped inner compartment 168 includes continuous verticalwalls and a ceiling. The walls of the inner compartment 168 are rigidlyattached to the outer wall 156 of the central compartment 20 by fourplastic bridges 170, 172, 174, 176 which appropriately partition thespace between the outer and inner walls for the four vertical sliders160, 162, 164, 166. The vertical sliders 160, 162, 164, 166 extend belowthe bottom of the inner compartment 168 and can be lowered to touch thescalp. Attached to the under surface of the ceiling of the innercompartment 168 is the disk pressure transducer 24, monitored bymicrocontroller 38.

The bladder 22 may be an inflatable bladder of Silastic® material, orother elastic material, contoured to fit closely within the spacecreated by the inner compartment 168 within the central compartment 20,the vertical sliders 160, 162, 164, 166, and the scalp. The verticalsliders 160, 162, 164, 166 function to provide a concentric, adjustable,inferior extension of the central compartment 20 down to the scalp, thuscreating a closed space for meaningful pressure measurements. Thebladder 22 is attached to a hollow tubing 178 which leads to the valve34, the solenoid pump 30, the valve 36, and the fluid reservoir 26.Additionally, there is a tube 180 that connects without a valve the backend of the solenoid pump 30 with the reservoir 26 to prevent thedevelopment of undesirable pressure differentials across the pumpplunger when the solenoid pump 30 is infusing or withdrawing fluid.

As shown, in one embodiment, the disk pressure transducer 24 may beattached to the ceiling of the inner compartment 168 to measure thepressure in the space of the central compartment 20 when the bladder 22has been inflated and clear pressure waveforms are detected bymicrocontroller 38. The disk pressure transducer 24 may include a sensorbelonging to displacement sensors, piezoresistive sensors, capacitivesensors, piezoelectric sensors, ultrasonic sensors, or optical sensors,for example.

In one embodiment, the four vertical sliders 160, 162, 164, 166 areindividually lowered by the care provider to make contact with thescalp, regardless of skull asymmetries or irregularities at the cranialvertex. It should be appreciated that in another embodiment more thanfour vertical sliders may be utilized to provide more accurate contactwith the scalp. In the present embodiment, each of the vertical sliders160, 162, 164, 166 extends up through the upper plate 106 of theapparatus 10 and has a handle so that it can be manually raised awayfrom or lowered down to touch the scalp adjacent to the fontanel F. Inanother embodiment, each vertical slider 160, 162, 164, 166 is raised orlowered by a micro-electric motor under the control of themicrocontroller 38. In both of these embodiments, the inferior edge ofeach vertical slider 160, 162, 164, 166 is covered with metal foil oranother conductive material that will not irritate the scalp to which asmall electric current is applied. As each vertical sliding member 160,162, 164, 166 is lowered to rest onto the scalp, the amperage of thefoil is monitored by the microcontroller 38. When the foil contacts theskin, the microcontroller 38 detects a significant change in electricalconductance (amperage) and causes a small green (or other color) LED tolight on the upper plate 106 next to the handle of its respectivevertical slider 160, 162, 164, 166. When all four vertical sliders 160,162, 164, 166 are in contact with the scalp, there will be four green(or other color) lights adjacent to the handles of the vertical sliders.

As noted, the inflatable bladder 22 fills the closed space of thecentral compartment 20, which is created when the vertical sliders areall in contact with the scalp. In one embodiment, the small discpressure transducer 24 is attached to the inferior surface of the innercompartment 168 ceiling, and pressure recordings are monitored by themicrocontroller 38. Initially, the controller 16 inflates bladder 22 byselectively working the valve 34 and the valve 36 to have the solenoidpump 30 infuse fluid from the fluid reservoir 26 into bladder 22 untilpulsations with distinct waveforms are detected by microcontroller 38.At this time, the pressure within the central compartment 20 closelyapproximates both the pressure in bladder 22 and ICP. Accordingly, ICPcan then be monitored continuously as long as apparatus 10 is notdislodged from its position on the head. Pressure and other physiologicdata can be wirelessly downloaded to a remote monitor.

In one embodiment, to modulate the intracranial pulse pressure byreducing PP in order to treat hydrocephalus, the microcontroller 38first determines representative measurements of pulse pressure. Themicrocontroller 38 then causes the solenoid pump 30 to selectivelywithdraw a small fluid volume from the bladder 22 during systole (asindicated by EKG or pulse oximetry data) and reinfuses this same volumeback into the bladder 22 during diastole. It is recalled that theintracranial pulse pressure is the arithmetic difference between thepeak pressure at systole and the lowest pressure during diastole.Withdrawal of fluid from bladder 22 during systole will reduce the peakintracranial pressure during systole, thereby reducing PP. In addition,re-infusing the fluid during diastole will increase the intracranialdiastolic pressure, also reducing PP. In other words, both actionsindependently and cumulatively reduce intracranial PP.

If the clinical situation were to require therapeutic augmentation ofthe intracranial PP such as to increase cerebral blood flow (CBF), forinstance, PP modulation would withdraw fluid from the bladder 22 duringdiastole, thereby lowering the diastolic pressure, and reinfuse thissame volume of fluid back into the bladder 22 during systole, therebyraising the systolic pressure. The cumulative effect would be toincrease the intracranial PP. In both cases, the infusion/withdrawalrates and volumes of fluid moved into or out of the bladder 22 by thesolenoid pump 30 are determined and controlled by microcontroller 38.

FIG. 22 depicts one embodiment of the compartment and the pressureregulator 14 in further detail in a hydraulic actuation application. Thepressure regulator 14 may include a dual-pump arrangement 200 havingconduit 202 between a fluid reservoir 204 and the pressure applicator88, which in one embodiment, may be a bladder 22 and a pressure sensor208. In one implementation, the pressure regulator 14 includes aninfusion fluid path 210 configured to permit introduction of fluid fromthe fluid reservoir 204 to the pressure applicator 88, which is depictedas the bladder 22. A drain fluid path 212 is configured to permitintroduction of fluid from the pressure applicator 88 to the fluidreservoir 204. It should be appreciated that the infusion fluid path 210and the drain fluid path 212 may at least partially overlap. An infusionpump 214 is disposed within the conduit 202 to permit urging of fluid onthe infusion fluid path 210 from the fluid reservoir 204 to the pressureapplicator 88. Similarly, a drain pump 216 is disposed within theconduit 202 to permit urging of fluid on the drain fluid path 212 fromthe pressure applicator 88 to the fluid reservoir 204. A valve 218 isdisposed in association with the infusion fluid path 210 with a valveelement 220 that selectively, under the control of the controller 16,resists fluid flow along the infusion fluid path 210. Correspondingly, avalve 218 is disposed in association with the drain fluid path 212 witha valve element 220 that selectively, under the control of thecontroller 16, resists fluid flow along the drain fluid path 212.

As previously discussed, the compartment 12 includes a pressureapplicator 88, shown as the bladder 22, fluidly coupled to the fluidreservoir 204 under the control of the pressure regulator 14. Thepressure applicator 88 is configured to selectively apply an externalpressure to the fontanel F. Further, as shown, the compartment 12includes the pressure sensor 208 configured to measure pressure at thefontanel F. In one embodiment, the pressure sensor 208 may include adisplacement sensor that measures displacement of the bladder 22. Aspreviously alluded, the pressure sensor 208 may include, however, asensor belonging to displacement sensors, piezoresistive sensors,capacitive sensors, piezoelectric sensors, ultrasonic sensors, oroptical sensors, for example. In hydraulic actuation applications, itshould be appreciated that the number and types of valves may vary aswell as the number and types of pumps, and reservoir style andplacement, among other hydraulic factors.

FIG. 23 depicts a further embodiment of the compartment 12 and thepressure regulator 14 in further detail, wherein a different approach istaken in order to adjust the fluid volume within the bladder 22 of thecentral compartment. This embodiment does not utilize a pump system toinfuse or withdraw fluid into or out of the bladder of the centralcompartment. Instead, the bladder 22 is deformed by mechanical actuationwith the movements of a micro-linear actuator 224 and a plunger 226 thatdirectly compress the bladder 22 within the closed space of the centralcompartment 20 to effect a bulging (or relaxation) of the bladder wallagainst the scalp of the fontanel. Reduced wattage requirements of themechanical system may prove superior to the pump system.

As shown, to achieve economy of space, the plunger 226 can serve as theceiling of the central compartment 20. The linear actuator 224 activelydisplaces the plunger 226 downward, utilizing a lever 228, fulcrum 230,concentric crank slider linkages 232, and gear 234 to compress thebladder 22; decompression occurs with the spring recovery movement ofthe linear actuator 224. The displacement volume can be adjusted bymoving the fulcrum 230 either closer to or farther away from the plunger226. Moving the fulcrum 226 forward would result in less compression ofthe central compartment bladder 226 with activation of the linearactuator 224. Positioning of the fulcrum 230 is achieved with the gear234, a miniature rack and pinion 236, a stepper motor 238, and thecontroller 16. In this mechanical system, the disk pressure transducer24 is located between the bladder 22 and the plunger 226 or the centralcompartment 22.

In contrast to the pump/valve arrangement to modulate intracranialpulsations, the embodiment of FIG. 23 utilizes mechanical deformation ofthe bladder 22 in order to alter the pulsatile changes of intracranialpressure with systole and diastole. A further alternative embodiment ofthe mechanical deformation approach is a micro-electric motor and a gearbox in the place of the linear activator.

Moreover, these embodiments that mechanically deform the bladder 22positioned over the fontanel F require only a small reservoir adjacentto the central compartment 20. A disc plunger may be positioned justbeneath the ceiling of the adjacent accessory reservoir, and this can belowered or raised with a threaded bolt and knob to displace fluid fromthe accessory reservoir through tubing leading to the bladder within thecentral compartment 20. It is envisioned that at the time ofmanufacture, both bladders and any intervening tubing be fully filledwith fluid that cannot traverse the walls of the bladders. In use, thecare provider first reviews recorded pressure tracings. A distinctwaveform indicates that the fluid volume appropriately fills theconfines of the system, and the measured pressure is a good estimate ofintracranial pressure. If there is no waveform, the care provider canlower the plunger within the accessory reservoir until a waveform isappreciated. If required, both bladders and connecting tubing can beremoved and replaced through access in the device floor. In addition,ports to the bladder of the accessory reservoir would allow the additionof fluid, if it were ever required.

Referring now to FIG. 24, within the housing 20, the controller 16,which may be the microcontroller 38, includes a processor 250, memory252, storage 254, inputs 256, and outputs 258 that are interconnected bya bus architecture 260 within a mounting architecture. The processor 250may process instructions for execution within the computing device,including instructions stored in the memory 252 or in storage 254. Thememory 252 stores information within the computing device. In oneimplementation, the memory 252 is a volatile memory unit or units. Inanother implementation, the memory 252 is a non-volatile memory unit orunits. Storage 254 provides capacity that is capable of providing massstorage for the computing device. Various inputs 256 and outputs 258provide connections to and from the computing device, wherein the inputs256 are the signals or data received by the apparatus 10, and theoutputs 258 are the signals or data sent from the apparatus 10.

As previously mentioned, a pressure sensor 90 measures pressure withinthe central compartment 20, which will approximate ICP when the bladder22 is inflated enough to record clear pressure waveforms. A transceiver262 is associated with the apparatus 10 and communicatively disposedwith the bus 260. The transceiver 262 may be internal, external, or acombination thereof to the housing 50. Further, the transceiver 262 maybe a transmitter/receiver, receiver, or an antenna for example.Communication between various devices in a hospital room, for example,and the apparatus 10 may be enabled by a variety of wirelessmethodologies employed by the transceiver 262, including 802.11, 3G, 4G,Edge, WiFi, ZigBee, near field communications (NFC), infrared (IR),Bluetooth low energy and Bluetooth, for example. The controller 16communicates with an ammeter 264, EKG interface, oxygen saturationinterface, passive positioning detection signals from multiplecapacitance position sensors, alarm interface indicating the device hasmoved, valve interfaces 268, solenoid pump interfaces 270, and displays70. The ammeter 264 receives low voltage current applied to the metalfoil on the inferior edges of each of the vertical sliders 160, 162,164, 166 that are lowered down to touch the scalp. Skin contact willmarkedly change the conductance, indicating that the vertical slidersare in appropriate position. In response, the controller 16 will turn onthe green (or other color) bulbs on the upper plate 106. The compartmentpositioning interface 266, which may include multiple capacitanceposition monitoring capability, will allow the care provider to alignthe apparatus 10 on the cranial sutures, and then monitor this baselinealignment in order to trigger a nursing alarm if the device 10 isdislodged. The valve interfaces 268 interface with valves 34, 36, forexample. These latter interfaces will open or close valve 34, connectingthe solenoid pump 30 to the bladder 22 while the valve 36 connecting thesolenoid pump 30 to the fluid reservoir 26 is reciprocally adjusted tobe open whenever valve 36 is closed and vice versa.

The memory 252 and the storage 254 are accessible to the processor 250and include processor-executable instructions that, when executed, causethe processor 250 to execute a series of operations. In one embodiment,the processor-executable instructions cause the processor 250 to send afirst control signal to the solenoid pump 30 to control the amount offluid in the inflatable bladder 22. The first control signal may includesignalization intended for the solenoid pump 30, the valves 34 and 36,or any combination thereof, by way of valve interfaces 268 and the pumpinterfaces 270. The processor-executable instructions may also cause theprocessor 250 to receive data relative to the pressure sensor 90, suchas, for example, the recording of pulsatile pressure with a clearwaveform from the inflatable bladder 22, thereby indicating pressurerecordings reasonably approximate ICP. In response to the evaluation,the processor-executable instructions may also cause the processor 250to send a second control signal to the solenoid pump 30 and valves 34and 36 to stop all infusions or withdrawals of fluid so that ICP and PPcan be recorded for a designated period of time; or the processor 250may respond to instructions by the care provider to begin PP modulationin order to decrease or increase the intracranial PP by a percentagedesignated by the care provider.

In some embodiments, the processor-executable instructions cause theprocessor 250 to receive data relative to intracranial pulse pressure atthe fontanel F from the pressure sensor 90 and evaluate the data todetermine intracranial pulse pressure and required pulse pressuremodulation, if any. The processor-executable instructions may then causethe processor to pulse pressure modulate. In one implementation, pulsepressure modulation may be achieved by the selectively withdraw of thepressure applicator from the fontanel during systole, and selectivelyextend the pressure applicator to the fontanel during diastole.

Referring now to FIG. 25, one embodiment is depicted of a method for useof the apparatus for the minimally-invasive, including non-invasive,treatment of hydrocephalus. At block 300, the methodology begins. Atblock 302, the position of the apparatus over the fontanel isestablished. At block 304, the position of the compartment isestablished and then locked at block 306. At block 308, fluid flow tothe compartment is established before actively modulating theintracranial pulsation at block 310. At block 312, the intracranialpulsation and PP is actively monitored. At decision block 314, if nochange in the intracranial pulsation is desired, then the methodologyreturns to block 310. On the other hand, if a change in the intracranialpulsation is desired, then at block 316 the fluid flow to thecompartment is calibrated before the methodology returns to block 310.

Referring now to FIG. 26, one embodiment is depicted of a method for useof the apparatus for the minimally-invasive, including non-invasive,monitoring and/or treatment of hydrocephalus. At block 330, the careprovider marks the metopic, sagittal, and both coronal sutures withmetallic ink. At block 332, the position of the apparatus over thefontanel is established to the microcontroller as baseline. At block334, the vertical sliders are lowered by the care provider to contactthe scalp, as indicated by four green lights. At block 336, the bladderis infused with fluid to fill the central compartment and expand gentlyagainst the skin over the fontanel until pulsations with clear waveformsare detected (block 338). At block 340, ICP and intracranial PP aremonitored by the apparatus. At block 342, the PP data may be downloadedto a monitor. At block 344, a mean pulse pressure value (AvPP) isdetermined over a designated period of time. At block 346, themicrocontroller 38 actively regulates the solenoid pump to modulateintracranial PP in order to reduce (or increase, if clinicallyindicated) PP by a designated percentage of the present PP (AvPP) asdetermined by the care provider. At block 342, these modulated PP dataare downloaded to a monitor. At block 348, the methodology to modulateintracranial PP in premature babies who have had IVH in order to preventthe development of post-hemorrhagic hydrocephalus may be somewhatdifferent than what has just been suggested, and this is summarized inFIG. 27.

Referring now to FIG. 27, in one embodiment of a clinical situation, atblock 360, the ICP and PP may be monitored daily for a designated periodof time, for example, 30 minutes. At block 362, the microcontrollerdetermines a mean PP, called AvPP_(TODAY). At block 364, themicrocontroller compares AvPP_(TODAY) to the last determination of meanPP, called AvPP_(PREVIOUS). The care provider may instruct themicrocontroller that AvPP_(PREVIOUS) refers to yesterday (block 366),one week ago (block 368), or, for example, every Monday (block 370),etc. Because it is expected that abnormal increases in PP will beobserved with the development of hydrocephalus, at block 371, a slidingscale of PP modulation responses can be established by the careprovider, as shown in the following example, illustrated in blocks 372,374, and 376 and summarized below.

At block 372, for AvPP_(TODAY)≥2 [AvPP_(PREVIOUS)], modulate mean PP byreducing AvPP_(TODAY) by some percentage (30% for example), set by thecare provider. At block 374, for AvPP_(TODAY)<2 [AvPP_(PREVIOUS)]but >0.9 [AvPP_(PREVIOUS)], modulate mean PP by reducing AvPP_(TODAY)some percentage (15% for example), set by the care provider. At block376, for AvPP_(TODAY)<0.9 [AvPP_(PREVIOUS)], do not modulate mean PP.

In another embodiment, the PP modulation sequence can gradually reducethe modulation effect over a designated time period, ultimatelywithdrawing all active influences on PP. In such a hydrocephalicpatient, who has responded to PP modulation with improvement in thehydrocephalic ventriculomegaly, gradually weaning of the degree of PPreductions while monitoring ICP and PP can serve as a functional test todetermine whether or not the hydrocephalic process has arrested. As anexample, if the treatment of hydrocephalus in a particular patient wereto reduce AvPP_(TODAY) by 30%, the “wean sequence” might be thefollowing:

a 25% reduction for one week,

a 20% reduction for the second week,

a 15% reduction for the third week,

a 10% reduction for the fourth week,

a 5% reduction for the fifth week, and

no reduction thereafter, but continued ICP and PP monitoring. If thepatient shows no ICP or PP abnormalities and ventricular size remainsstable, it would be reasonable to assume that the child indeed hasarrested hydrocephalus.

The order of execution or performance of the methods and proceduresillustrated and described herein is not essential, unless otherwisespecified. That is, elements of the methods and procedures may beperformed in any order, unless otherwise specified, and that the methodsmay include more or less elements than those disclosed herein. Forexample, it is contemplated that executing or performing a particularelement before, contemporaneously with, or after another element are allpossible sequences of execution.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is, therefore, intended that the appended claimsencompass any such modifications or embodiments.

What is claimed is:
 1. An apparatus for a minimally-invasive, including non-invasive, modulation of intracranial pressure, the apparatus comprising: a housing being sized for superjacent contact on a skull having a fontanel, the housing including an opening sized for the fontanel; the housing securing a compartment, a pressure regulator, and a controller therein; the controller being interconnected communicatively with each of the compartment and the pressure regulator; the compartment including a pressure applicator under control of the pressure regulator, the pressure applicator being configured to selectively apply an external pressure to the fontanel; the compartment including a pressure sensor configured to measure an intracranial pressure and an intracranial pulse pressure at the fontanel, the intracranial pulse pressure being an arithmetic difference between a peak pressure in systole and a lowest pressure in diastole; the controller receiving data relative to intracranial pressure and intracranial pulse pressure at the fontanel from the pressure sensor; the controller, if a clinical goal is at least one of to treat hydrocephalus and prevent hydrocephalus, selectively withdrawing the pressure applicator from the fontanel during systole and selectively extending the pressure applicator to the fontanel during diastole; and the controller, if the clinical goal is to increase cerebral blood flow, selectively extending the pressure applicator to the fontanel during systole and selectively withdrawing the pressure applicator from the fontanel during diastole.
 2. The apparatus as recited in claim 1, wherein the controller evaluates data to determine intracranial pulse pressure and required pulse pressure modulation.
 3. The apparatus as recited in claim 1, wherein the pressure applicator further comprises a bladder fluidly filled.
 4. The apparatus as recited in claim 3, wherein the bladder is selectively displaceable by hydraulic actuation.
 5. The apparatus as recited in claim 3, wherein the bladder is selectively displaceable by mechanical actuation.
 6. The apparatus as recited in claim 3, wherein the pressure sensor further comprises a disk pressure transducer that measures pressure within the bladder.
 7. The apparatus as recited in claim 1, wherein the pressure sensor further comprises a sensor selected from the group consisting of displacement sensors, piezoresistive sensors, capacitive sensors, piezoelectric sensors, ultrasonic sensors, and optical sensors.
 8. An apparatus for a minimally-invasive, including non-invasive, modulation of intracranial pressure, the apparatus comprising: a housing being sized for superjacent contact on a skull having a fontanel, the housing including an opening sized for the fontanel; the housing securing a compartment, a pressure regulator, and a controller therein; the controller being interconnected communicatively with each of the compartment and the pressure regulator; the compartment including a pressure applicator under control of the pressure regulator, the pressure applicator being configured to selectively apply an external pressure to the fontanel; the compartment including a pressure sensor configured to measure an intracranial pressure and an intracranial pulse pressure at the fontanel, the intracranial pulse pressure being an arithmetic difference between a peak pressure in systole and a lowest pressure in diastole; the controller receiving data relative to intracranial pressure and intracranial pulse pressure at the fontanel from the pressure sensor; the controller evaluating the data to determine intracranial pulse pressure and required pulse pressure modulation; the controller, responsive to evaluating the data, if a clinical goal is at least one of to treat hydrocephalus and prevent hydrocephalus, selectively withdrawing the pressure applicator from the fontanel during systole and selectively extending the pressure applicator to the fontanel during diastole; and the controller, responsive to evaluating the data, if the clinical goal is to increase cerebral blood flow, selectively extending the pressure applicator to the fontanel during systole and selectively withdrawing the pressure applicator from the fontanel during diastole.
 9. The apparatus as recited in claim 8, wherein the pressure applicator further comprises a bladder fluidly filled.
 10. The apparatus as recited in claim 9, wherein the bladder is selectively displaceable by hydraulic actuation.
 11. The apparatus as recited in claim 9, wherein the bladder is selectively displaceable by mechanical actuation.
 12. The apparatus as recited in claim 9, wherein the pressure sensor further comprises a disk pressure transducer that measures pressure within the bladder.
 13. The apparatus as recited in claim 8, wherein the pressure sensor further comprises a sensor selected from the group consisting of displacement sensors, piezoresistive sensors, capacitive sensors, piezoelectric sensors, ultrasonic sensors, and optical sensors.
 14. An apparatus for a minimally-invasive, including non-invasive, modulation of intracranial pressure, the apparatus comprising: a housing being sized for superjacent contact on a skull having a fontanel, the housing including an opening sized for the fontanel; the housing securing a compartment, a pressure regulator, and a controller therein; the controller being interconnected communicatively with each of the compartment and the pressure regulator; the compartment including a pressure applicator under control of the pressure regulator, the pressure applicator being configured to selectively apply an external pressure to the fontanel; the compartment including a pressure sensor configured to measure an intracranial pressure and an intracranial pulse pressure at the fontanel, the intracranial pulse pressure being an arithmetic difference between a peak pressure in systole and a lowest pressure in diastole; the controller receiving data relative to intracranial pressure and intracranial pulse pressure at the fontanel from the pressure sensor; the controller selectively withdrawing the pressure applicator from the fontanel during systole and selectively extending the pressure applicator to the fontanel during diastole.
 15. The apparatus as recited in claim 14, wherein the controller evaluates the data to determine intracranial pulse pressure and required pulse pressure modulation.
 16. The apparatus as recited in claim 14, wherein the pressure applicator further comprises a bladder fluidly filled.
 17. The apparatus as recited in claim 16, wherein the bladder is selectively displaceable by hydraulic actuation.
 18. The apparatus as recited in claim 16, wherein the bladder is selectively displaceable by mechanical actuation.
 19. The apparatus as recited in claim 16, wherein the pressure sensor further comprises a disk pressure transducer that measures pressure within the bladder.
 20. The apparatus as recited in claim 14, wherein the pressure sensor further comprises a sensor selected from the group consisting of displacement sensors, piezoresistive sensors, capacitive sensors, piezoelectric sensors, ultrasonic sensors, and optical sensors. 